At least three Liberian gunmen were killed by Marine guards Tuesday when they tried to invade the U.S. Embassy compound as factional fighting and lawlessness swept Monrovia after the breakdown of a 10-day-old cease-fire, U.S. officials reported.

The Pentagon said unidentified Liberian assailants fired on the embassy on three occasions, drawing return fire from the Marines. An official said three to six gunmen were killed and that at least one other was wounded.

One of the Marine defenders was slightly injured, possibly by debris kicked up by a bullet or by an expelled shell casing, the Pentagon said. He did not require medical treatment.

Fighting in Liberia’s bloody, 6-year-old civil war resumed Monday when a cease-fire, imposed April 19, collapsed.